# The Naked Scientists Forum

### Author Topic: What is the volume of the universe?  (Read 5474 times)

#### harwoodj

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##### What is the volume of the universe?
« on: 15/10/2011 20:01:03 »
john ludley  asked the Naked Scientists:

I am trying to calculate the volume of the universe, but have a problem. Although we can calculate the volume of, say, a house in cubic metres, I am stumped by the 4-dimensional aspects of the universe.

We believe that the farthest distance between any two points in the universe is 13.5 B light years.  But using the balloon analogy, this isn't the radius of the universe.  In fact continuing the analogy, the farthest distance between two points on a balloon (call it *F*) is* Î .R* where* R* is the radius through the balloon, and the area of the balloon is* 4.Î .R2* ,  or expressing *R* in terms of* F, ** 4.F2/ Î .  * Can we extend the analogy into a 3-D space and say the volume of the universe is * 4/3.Î .R3* , which using the same relationship between* F* and* R* gives* 4/3. F3/Î 2 * .  I doubt it is that simple.

So what is the volume of the universe?

John Ludley

What do you think?
« Last Edit: 15/10/2011 20:01:03 by _system »

#### Airthumbs

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##### What is the volume of the universe?
« Reply #1 on: 15/10/2011 23:42:12 »
You might be able to calculate the volume of the visible Universe but as for the entire Universe I am not so sure about that...... if there is a way to do this, I would be very interested so look forward to more posts on this subject..

#### DarkSun

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##### What is the volume of the universe?
« Reply #2 on: 25/10/2011 05:22:29 »
How is the universe only 13.7 billion years old, when the radius is 25 billion light years wide?
That would mean that the universe has expanded faster than the speed of light, which is improbable. I would also highly doubt that it expands anywhere near that fast. Or do they mean that it would take 25 billion light years to get back to the center of the universe from the outer edge due to the continued expansion of the universe? If so then that isnt a true indication of how wide the universe is at this present time. Any thoughts? newbielink:http://www.panqp.com/ [nonactive]
« Last Edit: 31/03/2014 09:27:22 by DarkSun »

#### Don_1

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##### What is the volume of the universe?
« Reply #3 on: 25/10/2011 10:26:53 »
Since the universe is without boundaries, except that which we define as the 'known' universe, I would say it cannot be measured.

Its a bit like asking the volume of the outside of a ball.

#### imatfaal

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##### What is the volume of the universe?
« Reply #4 on: 25/10/2011 12:50:10 »
How is the universe only 13.7 billion years old, when the radius is 25 billion light years wide?
That would mean that the universe has expanded faster than the speed of light, which is improbable. I would also highly doubt that it expands anywhere near that fast. Or do they mean that it would take 25 billion light years to get back to the center of the universe from the outer edge due to the continued expansion of the universe? If so then that isnt a true indication of how wide the universe is at this present time. Any thoughts?

Darksun - this measurement (although i dont really recognize the 25 Gly) does come down the idea of continued expansion as you mentioned.  We have fairly good evidence for this continued and accelerated expansion - not least the wavelength of the cosmic background.  The light that is reaching us now - and has been travelling for 13.7ish Gy was emitted from objects/areas of space that are much further away than 13.7Glyr - the figure of 44Gly springs to mind but I am not sure without checking. Light that is being emitted as I type will reach us in well over 13Gy in fact well over 40Gy - so not much chance of anyone being around to check!

Oh and Welcome to the forum!

#### harwoodj

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##### What is the volume of the universe?
« Reply #5 on: 28/10/2011 15:08:12 »
Interesting comments.  Wikipedia offers several sizes from 44Gly (billion light-years) to about  80Gly.  But, importantly discriminates between 'the Universe' and the 'Observable Universe' which depends on where you are standing! - perhaps this leads to the 4-D aspects of the Universe.  Let's hope that the next podcast handles this subject.  (Incidentally, in my first published comment, π (pi) had been converted to I^ which may have puzzled some.  John Ludley

#### imatfaal

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##### What is the volume of the universe?
« Reply #6 on: 31/10/2011 10:08:44 »
Interesting comments.  Wikipedia offers several sizes from 44Gly (billion light-years) to about  80Gly.  But, importantly discriminates between 'the Universe' and the 'Observable Universe' which depends on where you are standing! - perhaps this leads to the 4-D aspects of the Universe.  Let's hope that the next podcast handles this subject.  (Incidentally, in my first published comment, π (pi) had been converted to I^ which may have puzzled some.  John Ludley

Hello John - as far as we know (and avoiding speculation of universe that is not FLRW ie non isotropic - cosmological principle) then the observable universe is about 44Gly radius sphere from where-ever you are in the universe.  Its all the stuff that information travelling at light speed can reach us now (and the same applies for any other point you choose).  Knowledge of the universe is scant - knowledge of the observable universe is less scant but still pretty hazy, but there exists the chance of empirical observation and prediction for the observable, the entire universe can only really be guessed and hypothesised about.

FYI if you want to use Greek Letters (and a very small set of symbols then hit the preview post button and they become available in the full editor.  Π π - and hopefully these will be correctly rendered

#### neilep

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##### What is the volume of the universe?
« Reply #7 on: 31/10/2011 10:33:20 »
Armed with my trusty ruler I spent all night calculating the volume of the universe and I have deduced that it is big !

#### imatfaal

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##### What is the volume of the universe?
« Reply #8 on: 31/10/2011 10:47:39 »
Armed with my trusty ruler I spent all night calculating the volume of the universe and I have deduced that it is big !

Empirical science at its best - you are a source of inspiration to us all

#### Bored chemist

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##### What is the volume of the universe?
« Reply #9 on: 31/10/2011 21:40:37 »
It's my understanding that the mathematical definition of the word "very" is that if X is small then X^2 is very small.
Since the radius of the universe (as measured by our friend with his trusty ruler) is big this would suggest that the area of the universe is very big.
However I think that, by using the same idea again we would find that, to count as very very big, something would have to be the 4th power of something big. So the volume universe (being the third power of something big)  is, apparently

somewhere between very big and very very big.

#### CZARCAR

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##### What is the volume of the universe?
« Reply #10 on: 31/10/2011 22:20:33 »
universe aint pretty big, its just pretty

#### CPT ArkAngel

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##### What is the volume of the universe?
« Reply #11 on: 01/11/2011 00:17:59 »
Especially women...

The Universe might be quite "big". I wonder how big is infinite...?

"Eternity is really long, especially near the end." ... Woody Allen Quote

#### neilep

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##### What is the volume of the universe?
« Reply #12 on: 01/11/2011 10:07:26 »
Armed with my trusty ruler I spent all night calculating the volume of the universe and I have deduced that it is big !

Empirical science at its best - you are a source of inspiration to us all

#### imatfaal

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##### What is the volume of the universe?
« Reply #13 on: 01/11/2011 11:28:52 »
Armed with my trusty ruler I spent all night calculating the volume of the universe and I have deduced that it is big !

Empirical science at its best - you are a source of inspiration to us all

And using the BC protocol of bigness its ve very big

#### The Naked Scientists Forum

##### What is the volume of the universe?
« Reply #13 on: 01/11/2011 11:28:52 »